Reproductive energetics of the tropical, oceanic copepod, Euchaeta rimana Bradford.

摘要

Reproduction by the carnivorous copepod Euchaeta rimana was examined using the Edmondson egg ratio technique in field samples and laboratory experiments designed to determine its limiting factors.; Egg production samples were collected on three cruises in three distinct geographic areas: the oligotrophic central South Pacific, the windward coast of the island of Hawaii, and a transect from Alaska to Hawaii. Hydrographic conditions significantly influenced the distribution and egg production rates of E. rimana on two cruises. On the South Pacific cruise, water column disturbances associated with breaking internal waves were followed by a period of increasing egg production. On the Alaska to Hawaii transect, the Subtropical Convergence was the northern limit of E. rimana's distribution, and the site of the highest recorded egg production (5 eggs female{dollar}sp{lcub}-1{rcub}{dollar} day{dollar}sp{lcub}-1{rcub}).{dollar}; When compared to laboratory maxima, low secondary production rates of field-captured females were observed. Field production averaged only 10% of female body carbon per day, compared to a laboratory maximum of 25% of female body carbon per day.; Limitation of egg production by food or mates was examined. Both hypotheses contributed to an understanding of the data, and neither hypothesis could be eliminated.; A method of determining in situ feeding rates was developed using fecal pellets as a feeding index, but insufficient precision was obtained to be useful. An assimilation efficiency of 92% was observed.; Respiration was measured using a variation of the polarographic electrode method, which corresponded well to both bottle incubations and the results of previous studies. Respiration accounted for 25% of the female body carbon per day. Summing respiration, production, and egestion produced a minimum ingestion of 27 {dollar}mu{dollar}g carbon female{dollar}sp{lcub}-1{rcub}{dollar} day{dollar}sp{lcub}-1{rcub},{dollar} which was approximately equal to twice the rate obtained by the fecal pellet method.; Using the calculated ingestion rate from the budget equations and natural prey concentrations, the females cleared 18 to 88 liters female{dollar}sp{lcub}-1{rcub}{dollar} day{dollar}sp{lcub}-1{rcub},{dollar} depending on the mean prey body mass consumed. Such huge volumes cleared were not obtained in large volume laboratory feeding experiments. Microscale prey patchiness and copepod behavior are believed to be critical to the survival of E. rimana.